diff --git a/plugins/sudoers/regress/parser/check_base64.c b/plugins/sudoers/regress/parser/check_base64.c
index 4fe54ade5..b7f6098f2 100644
--- a/plugins/sudoers/regress/parser/check_base64.c
+++ b/plugins/sudoers/regress/parser/check_base64.c
@@ -28,8 +28,8 @@
 #include <sudo_util.h>
 
 /* From parse.h */
-extern size_t base64_decode(const char *str, unsigned char *dst, size_t dsize);
-extern size_t base64_encode(const unsigned char *in, size_t in_len, char *out, size_t out_len);
+extern size_t base64_decode(const char * restrict str, unsigned char * restrict dst, size_t dsize);
+extern size_t base64_encode(const unsigned char * restrict in, size_t in_len, char * restrict out, size_t out_len);
 
 sudo_dso_public int main(int argc, char *argv[]);